Multi-phase SMPS is used for providing high current in applications of, for example, microprocessors. FIG. 1 schematically shows a prior art multi-phase SMPS 100. The multi-phase SMPS 100 comprises N switching circuits P1-PN sharing a common input Vin and a common output Vout. The output Vout provides power supplied to a load. Each switching circuit, e.g. switching circuit P1 comprises a switch S1 and switching circuit P1 provides current to the load under the switching action of the corresponding switch S1. Switches S1 to SN are turned on sequentially by a plurality of control signals. However, during load up-transient, SMPS 100 can not offer enough current by sequentially turning on the switches anymore. Accordingly, a method of transient control in multi-phase SMPS is desired. It is further desired that the transient control can be adapted to the different levels of load transient.